1. Field of the Invention
The present invention relates to a precision adjustment/drive device, and more specifically to a device for performing fine adjustment on the orientation of an optical element (such as a lens or a mirror) of an exposure device used in the process of manufacturing a semiconductor or a liquid crystal device. In more detail, such orientation adjustment is performed during image formation in which an image on an original (e.g. a mask, a reticle, or the like) is projected to a target object. (e.g. a wafer) through exposure by using the optical element, for effecting the image formation with enhanced accuracy.
It is to be noted that, other than for the optical element adjustment described above, a mechanism described in the present invention can be used for performing 6-axis scanning of a movable portion such as a workpiece of a three-dimensional measurement instrument or a machine tool, a precision moving table, or a specimen mount of a microscope.
2. Related Background Art
A semiconductor exposure device is a device for transferring patterns on an original (reticle) having many different kinds of patterns formed thereon to a silicon wafer (base). For preparation of a high-density circuit, not only resolution performance but also enhanced accuracy of superposition is essential. A superposition error in semiconductor exposure devices is classified into an alignment error, an image distortion, and a magnification error. An alignment error can be mitigated by adjusting relative positions of the original (reticle) and the base (wafer) with respect to each other. On the other hand, an image distortion and a magnification error can be mitigated by moving a part of the optical elements of an optical system. When moving an optical element in the direction of the optical axis, care needs to be taken so that an error in the amount of movement in the movement direction of the optical element, and movement components in directions other than the movement direction, in particular a positional deviation (referred to as “parallel eccentricity”) in a direction orthogonal to the optical axis of the optical element and a tilt of the optical element (referred to as “tilt eccentricity”), do not become large.
As a conventional optical element moving device for use in semiconductor exposure devices, there has been devised one as described in Japanese Patent Application Laid-Open No. 2000-357651 which employs a mechanism using a parallel flat spring.
FIGS. 16A and 16B are respectively a sectional view and a top view of the conventional optical element moving device. As shown in the figures, the conventional optical element moving device includes: a movable table 1 for retaining an adjusting lens 7 for adjusting the magnification, abberration, and the like of an optical system, and a cell 8 for supporting the adjusting lens 7; and a stationary table 2 constituting a part of a stationary portion of a projection optical system. A ring-shaped flat spring 11 is fixed to both end faces of the movable table 1 and the stationary table 2 so as to seal both the end faces. The movable table 1 has a cylindrical configuration, and a diameter of its upper surface is different from that of its lower surface. Likewise, the stationary table 2 also has a cylindrical configuration, and an inner diameter of an opening in its upper surface is different from that of an opening in its lower surface. The stationary table 2 has at least one hole, and is thus capable of changing the position of the movable table 1 by changes in the pressure or volume of a drive fluid.
As another conventional example, there is an optical element fine adjustment device as disclosed in U.S. Pat. No. 5,986,827. However, the structure disclosed therein allows fine adjustment in only three axes, and does not allow adjustment within the plane of an optical element, making the device inadequate for applications which require high-precision adjustments on the position and orientation of an optical element.
As still another conventional example, there is one disclosed in Japanese Patent Application Laid-Open No. 2002-131605. However, the device disclosed therein employs a contraction mechanism using a long-arm lever (the distance from the fulcrum to the point of application or the point of action is long), and thus it is expected that the device has a low natural frequency. When the natural frequency is low, vibrations from the exterior of the device are transmitted to a movable portion, which is not only unpreferable for high-precision position and orientation adjustments but also makes it difficult to perform high-speed drive.
With the invention disclosed in Japanese Patent Application Laid-Open No. 2000-357651, parallel eccentricity and tilt eccentricity components, generated in accordance with movement of an optical element, are dependent on the accuracy of guiding by a flat spring guide. In addition, the initial position and the orientation of the optical element are dependent on the assembling accuracy of the device. However, as semiconductor device patterns become increasingly fine, optical elements are increasingly required to realize higher position accuracy, higher orientation accuracy, and higher drive position positioning accuracy for correction of aberrations etc, than conventionally required. For this reason, the devices as disclosed in Japanese Patent Application Laid-Open No. 2000-357651 and U.S. Pat. No. 5,986,827, which perform only one-axis drive and three-axis drive, respectively, are inadequate and a device capable of performing adjustment along three orthogonal axes in a translational direction and also about three axes in the translational direction, thus in 6 axes in total, is being demanded.
Further, in order to mitigate positional displacement of an optical element due to vibrations entering from the exterior of the device, high rigidity is required of the above 6-axis adjustment mechanism at the same time.
In view of the above, an object of the present invention is to provide a drive mechanism or a positioning mechanism which is capable of performing fine adjustment in 6 axis directions and has high rigidity.